Won't connect to PC, not showing up in device manager

Hi guys,

I bought a damaged iPhone 7 from my sister recently and tried to repair it. Replaced the lightning connector assembly, the loudspeaker and the screen.

It's back together and seems to be working fine, but the iPhone is disabled and I have to connect it to iTunes to fix it. When I plug it into my computer (or my Mac, or her Mac) it will vibrate when you plug it in, but that's all. No charging, no connecting. It doesn't show up in device manager. It will charge no problem from the wall.

Is this the U2 USB IC problem I'm having? I'm not sure if this is my fault, or if it was broken before. One of my friends is very skilled at soldering and I'm sure he'd be able to replace the IC if I asked him very nicely and we were sure that would fix it.

Anyone know what I should do?

Cheers